With its icy surface, Neptune's moon Triton is one the coldest objects in the solar system. It is also the largest of Neptune's moons. Ice volcanoes spout what is probably a mixture of liquid nitrogen, methane and dust, which instantly freezes and then snows back down to the surface.
This view of the moon was captured by Voyager 2 during its flyby in 1989.
Image credit: NASA/JPL